Simultaneous Wastewater-to-Hydrogen Upgrading via Mechanically Driven Piezocatalysis Over Ag-ZnO Nanorods.

The growing demand for sustainable hydrogen production has driven increasing interest in wastewater as a resource for simultaneous pollutant removal and energy recovery. However, most existing wastewater-to-hydrogen approaches rely on external electricity, light, or chemical agents, underutilizing mechanical energy and inherent charge complementarity. Here, a piezocatalytic upgrading strategy is developed to couple organic pollutant degradation with hydrogen evolution in a single mechanically driven system. Zinc oxide nanorods serve as the piezoelectric platform, while surface-engineered silver regulates interfacial charge extraction and directional utilization. Under mechanical excitation, piezoelectric polarization generates complementary charges that drive oxidative pollutant degradation and reductive hydrogen evolution. Using rhodamine B as a model contaminant, the Ag-modified ZnO nanorods deliver a 90.8% increase in hydrogen yield and a 339% enhancement in degradation kinetics compared to pristine ZnO. Notably, the system demonstrates versatile applicability across various classes of pollutants and real-water matrices, maintaining efficient upgrading performance under ambient atmosphere and low-intensity mechanical stirring. Combined experimental and theoretical results reveal that the Ag interface enhances charge separation, water activation, and hydrogen adsorption energetics. This work establishes a dual-functional piezocatalysis paradigm for scalable wastewater-to-hydrogen upgrading.